Ferdinand and the Cardinal enter with the letter, and Ferdinand says he has dug up a mandrake, which is known as being both an aphrodisiac and a poison. Ferdinand says he is growing mad and he shows the Cardinal the letter, saying that their sister is damned, and that she has “grown a notorious strumpet.” Ferdinand becomes increasingly enraged, threatening to make her bleeding heart a sponge. When the Cardinal asks why he’s getting so upset, Ferdinand continues in his rage, saying he wishes he could be the one to “root up her goodly forests” and “lay her general territory as waste.”
Ferdinand is completely enraged by the information that his sister is officially, in his opinion, a whore. His desire to “root up her goodly forests” and “lay her general territory as waste” are both violent threats and sexual innuendos, as forests and gardens are common images for the female body, and “lay her” has clear sexual implications. Ferdinand’s incestuous desire is on display here, and jealousy therefore emerges as another possible motive for his rage.
The Cardinal asks if their royal blood will be tainted, wondering who the father of the Duchess’s child might be, and Ferdinand says they must use drastic measures “to purge infected blood.” He says that he’ll have the Duchess cut to pieces, and the Cardinal curses nature for placing women’s hearts on their left side (which supposedly made them sinister). Ferdinand curses men for being so foolish as to trust women and he describes the Duchess as a laughing hyena. Ferdinand asks his brother to talk to him before his imagination leads him to see her in the act of sin.
The Cardinal is worried that their royal bloodline will be tainted (or, as Ferdinand puts it, infected) by the introduction of lesser blood through a lower class father, but he is also worried that his own reputation and honor are threatened by the Duchess’s actions. We can note that Ferdinand seems very aware that he is now liable to commit a serious sin.
Ferdinand starts imagining who the Duchess’s lover might be. When the Cardinal tries to calm him, Ferdinand says that it’s “not your whore’s milk that shall quench my wild fire, / But your whore’s blood!” The Cardinal says that this rage is much too loud, and that it is deforming Ferdinand and making him beastly.
Ferdinand proclaims that the only way to calm himself down is to spill the Duchess’s blood—we see that anger has the power to deform humans and animalize them, foreshadowing Ferdinand’s supposed werewolf condition later in the play.
Ferdinand then calms down and says he will study calmness and practice seeming calm even though he is still enraged. He says he could kill the Duchess now by killing himself or the Cardinal, since he thinks that the Duchess’ disobedience is heaven’s revenge on the brothers for their sins. Ferdinand, still overcome with rage, promises such a horrible and gruesome vengeance against the Duchess that the Cardinal threatens to leave. But Ferdinand says that he’ll calm down, and that, until he knows who is sleeping with the Duchess, he’ll do nothing.
Ferdinand continues to practice what seems to be the defining characteristic of corruption: cultivating an appearance that’s at odds with reality. He also posits a theory that the Duchess’ disobedience is actually a punishment to the brothers from heaven, not a legitimate choice. In this way he questions the righteousness of his own actions, but he also robs the Duchess of any agency.